Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

281
FXUS63 KLOT 031126
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
626 AM CDT Fri Apr 3 2026

.KEY MESSAGES...

- There is another threat of severe storms mainly south of I-80
  later this afternoon, and across the area this evening and
  overnight. Isolated large hail and damaging winds are the main
  threat, though an isolated tornado threat will exist late
  this afternoon and early evening in the south.

- A transition toward a quieter, but cooler, pattern is on track
  to arrive Sunday through early next week before milder and
  more active weather returns for the second half of the week.

&&

.DISCUSSION...
Issued at 353 AM CDT Fri Apr 3 2026

Through Thursday:

Surface low pressure was analyzed over the Straits of Mackinac
early this morning, with a trailing cold front extending through
northwest IN and east-central IL. Only a few isolated showers
linger across our far southeastern cwa in advance of the front
at this hour, and these will move out of the area shortly as the
cold front continues to push off to the east. Behind the front,
blustery west surface winds were pulling cooler air into the
region (low-mid 40s upstream in eastern IA) along with an
extensive area of stratus. Surface ridging noted across central
IA will move east into the area later this morning in response
to strong subsidence (indicated by 80-100 meter H5 height rises)
in the wake of the departing mid-level short wave and surface
low, allowing winds to quickly diminish as well as likely
eroding some holes in the shallow stratus deck with time today.

Farther west however, another strong mid-level wave/closed low
was evident in GOES vapor imagery over WY. This disturbance will
propagate east across the High Plains by midday, inducing
renewed low-level return flow and warm advection across the mid-
Mississippi Valley and western Great Lakes by this afternoon
ahead of a new surface low expected to develop into southwest
IA/northwest MO by this evening. In response, the trailing
portion of the aforementioned cold front will lift back north
into our southern cwa (to the south of a Pontiac-Rensselaer
line) as a warm front late this afternoon. As the warm front
lifts north this afternoon, CAM guidance indicates a chance of
isolated to scattered thunderstorm development along the
boundary as warm/moist/conditionally unstable low-level air mass
returns. Deep-layer shear of 35-40 kts and modestly-steep (~7
C/km) mid-level lapse rates appear to support storm
organization including some supercellular modes, while backed
south-southeast low-level winds and 0-2 km speed/directional
shear in the vicinity of the boundary may support an isolated
tornado threat near the warm front late this afternoon into
early this evening across our southern tier of cwa counties or
so. SPC has nudged the Day 1 Slight (level 2 of 5) severe and 5%
tornado risk into our far south/southwest cwa in association
with this threat.

The upper low/short wave is progged to lift northeast across
the upper Midwest overnight into Saturday morning, with its
attendant surface low currently progged to track across the
IL/WI border region around daybreak Saturday. The warm front
thus lifts across much of the forecast area tonight, followed
closely by the eastward moving cold front early Saturday
morning. Scattered thunderstorms are expected to increase in
coverage ahead of this system this evening/overnight, with more
of a large hail/isolated damaging wind threat (SPC marginal, or
level 1 of 5 severe risk). Unseasonably high PWATS ~1.50" will
support locally heavy rainfall with some of these storms as
well, and we`ll have to keep an eye on localized flooding
potential especially across portions of northern IL where MRMS
estimated rainfall of 2.50-3.50 inches fell Thursday/Thursday
night. Lingering showers should move out of the area shortly
after daybreak Saturday morning, as the cold front continues to
march to the east, though a few wrap-around light showers or
sprinkles may develop beneath the upper trough axis in the
afternoon.

In response to the surface low developing west of the area
today, surface winds will turn easterly across far northern IL.
This will set up a significant temperature gradient with highs
only around 50 along the IL lake shore, and lower 60s well-
inland. Farther south where the warm front returns this
afternoon, temperatures will likely warm into the low-mid 70s.
Temperatures will likely warm from south to north overnight
(especially across northeast IL and northwest IN) as the warm
front continues to lift north ahead of the low. The temp roller
coaster then continues, as temps gradually fall into the 50s and
upper 40s behind the cold front Saturday.

A period of more tranquil weather conditions appears to be in
store for the region Sunday through early next week, as an
expansive area of surface high pressure gradually builds east
through the area. It will remain cooler than normal (with
blustery northwest winds lingering Sunday), before trending
milder and more active again mid-late week.

Ratzer

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 626 AM CDT Fri Apr 3 2026

Key Aviation Messages for the current TAF period:

- MVFR cigs expected through the most of the TAF period.
  Localized IFR cigs are possible tonight during heavier
  downpours.

- West winds become east by midday.

- Scattered showers and storms, with gustier easterly winds,
  are expected late this afternoon through the overnight. There
  is a 30 percent chance for storms Friday evening.

- Gusty Southwest winds are expected Saturday morning with drier
  conditions.

A blanket of MVFR cigs cover the region this morning. Winds
remain out of the west this morning. Isolated gusts between 15
to 20 knots are possible, but not frequent enough for formal
mention in the TAF. As a warm front starts to move northward
through central Illinois around midday, winds are expected to
turn to the east, with some lake enhancement pushing it farther
inland through the afternoon. While KRFD might entertain a brief
window in the afternoon of VFR cigs, opted to keep the Chicago
TAF sites with MVFR cigs, though there is a non-zero chance that
cigs briefly go IFR in the afternoon with the lake enhanced
easterly winds.

As that warm front approaches after 00Z, showers and gusty
easterly winds are expected across the airspace and remain
through the overnight. The chances for embedded thunder are
along the warm front this evening with diminishing chances after
midnight. MVFR cigs are expected with this front with a chance
for IFR during heavier downpours. As a surface low enters
western Illinois toward daybreak, winds will diminish and
directions become variable depending upon the track of the
surface low, as showers continue through daybreak. As a cold
front moves through after 12Z, showers are expected to diminish
and winds switch to the southwest with increasing gusts over 20
knots.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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